Polycarbonate resins are prepared by condensation-polymerization of an aromatic diol such as bisphenol A with a carbonate precursor such as a phosgene and have excellent impact strength, dimensional stability, heat resistance and transparency. Thus, the polycarbonate resins have application in a wide range of uses, such as exterior materials of electrical and electronic products, automobile parts, building materials, and optical components.
Recently, in order to apply these polycarbonate resins to more varied fields, many studies have been made to obtain desired physical properties by copolymerizing two or more aromatic diol compounds having different structures from each other and introducing units having different structures in the main chain of the polycarbonate.
Especially, studies for introducing a polysiloxane structure in a main chain of the polycarbonate have been undergone, but most of these technologies have disadvantages in that production costs are high and a chemical resistance or impact strength, particularly impact strength at low-temperature are increased, but melt index is conversely reduced.
Given the above circumstances, the present inventors have conducted extensive studies to overcome the drawbacks encountered in the prior arts and develop a copolycarbonate with improved physical properties such as impact strength at room temperature, impact strength at low-temperature and melt index, and found that a copolycarbonate in which specific siloxane compounds are introduced in the main chain of the polycarbonate as described below satisfies the above-described properties. The present invention has been completed on the basis of such a finding.